1. Field of the Invention
The present invention relates to an antireflection film used in order to suppress decrease of the screen visibility of a visual display, such as in liquid crystal displays (LCD), organic EL displays and PDP, and to an optical element having the antireflection film concerned prepared thereto. Moreover, the present invention also relates to a visual display with the antireflection film or the optical element concerned provided thereto. Furthermore, it relates to an antireflection layer forming agent, and an antireflection layer formed by the antireflection layer forming agent.
2. Description of the Prior Art
Research and development in recent years, a liquid crystal panel device is ensuring steadfast status as a display. However, in monitors for car navigation system and in monitors for video cameras, which is used with high frequency in brightly illuminated environment, decrease in visibility caused by surface reflection is notably observed. Therefore, it is becoming indispensable that antireflection processing is applied to polarizing plates used for liquid crystal panel devices. Polarizing plates with antireflection processing applied thereto is used for most of liquid crystal displays having high operating frequency in outdoors.
Generally in antireflection processing, multi-layer laminated body of two or more thin films comprising materials having different refractive indexes is produced by dry processing methods, such as vacuum deposition method, sputtering method, and CVD method, and thus design is adopted for reducing reflection of visible light region as much as possible. However, in formation of thin film by the above-mentioned dry processing, a vacuum facility is required, consequently leading to very expensive processing costs. Therefore, in recent years, antireflection films are produced to which antireflection processing is performed by formation of antireflection film by a wet coating process. In antireflection films, a constitution comprising, a transparent substrate used as substrate/a resin layer for granting hard coat property/an antireflection layer with low refractive index, is usually adopted. In these antireflection films, in the viewpoint of reflectance, a hard coat layer requires a higher refractive index and an antireflection layer requires a lower refractive index.
As a material having a low refractive index for forming the above described antireflection layer, in the viewpoint of refractive index or stain resistance, polymers containing fluorine etc. are used. Moreover, in general, some approach is performed where porous structures are obtained utilizing a sol-gel reaction of alkoxy silanes or organo alkoxy silanes as material giving a lower refractive index to provide a lower refractive index. However, in the above-mentioned sol-gel reaction, when baking at low temperature is performed in order to control reactivity and to obtain porous structure, long reaction period is inevitably required in curing process, and consequently an antireflection layer having sufficient scratch-proof property cannot be formed in a short period of time. Moreover, film surfaces given by the above-mentioned sol-gel reaction have problems also in stain resistance.
Moreover, in Japanese Patent Laid-open Publication No. H9 (1997)-208898, a proposal using fluorine compounds containing a polysiloxane structure for an antireflection layer is disclosed. In formation of an antireflection layer with the fluorine compounds, uniform reaction is performed, and this method is excellent in stability of liquid, and film uniformity after cured, and good also in stain resistance. However, the fluorine compounds have a little slow curing rate of reaction, and therefore curing requires a long period of time in baking at low temperature. Baking at high temperature is not acceptable, for example, as in a case where triacetyl cellulose film preferably utilized as a protective film of polarizing plate is used as a transparent substrate, and an antireflection layer with the above described fluorine compounds is formed through a hard coat layer thereon. Curing (ageing) time of several days at a temperature of approximately 100 degree C. is required in order to obtain sufficient scratch-proof property.